Rotary bit for hydraulically drilling holes into underground formations

ABSTRACT

A jet rotary drill bit having a number of nozzles for jetting drilling fluid against the bottom of a well borehole, the centers of the jet nozzles being arranged in circles and at selected spaced intervals, and each nozzle having a central axis directed in a line to cross the central axis of the bit body at an angle other than 90*.

United States Patent Pols et al. May 6, 1975 [54] ROTARY BIT FOR HYDRAULICALLY 3,384,192 5/1968 Goodwin et al. 115/422 3,548,960 12/1970 115/393 DRILLING HOLES INTO UNDERGROUND FORMATIONS Inventors: Albert C. Pols; Robijn Feenstra,

both of Rijswijk, Netherlands Assignee: Shell Oil Company, Houston, Tex.

Filed: Feb. 25, 1974 Appl. No.: 445,395

U.S. Cl. 175/393; 175/67; 175/339; 175/422 Int. Cl E2lb 7/18 Field of Search 175/339, 340, 393, 422; 299/31 FOREIGN PATENTS OR APPLICATIONS 252,969 3/1966 U.S.S.R 175/340 Primary Examiner-Frank L. Abbott Assistant ExaminerRichard E. Favreau [57] ABSTRACT A jet rotary drill bit having a number of nozzles for jetting drilling fluid against the bottom of a well borehole, the centers of the jet nozzles being arranged in circles and at selected spaced intervals, and each nozzle having a central axis directed in a line to cross the central axis of the bit body at an angle other than 90.

2 Claims, 9 Drawing Figures MENTEUHAY ems "-1.881 .561

SHEET 18F 2 FIG.2

ROTARY BIT FOR I-IYDRAULICALLY DRILLING HOLES INTO UNDERGROUND FORMATIONS BACKGROUND OF THE INVENTION The present invention relates to a rotary bit for drilling holes into underground formations and penetrating into deep-lying substrata with the object of recovering therefrom valuable materials, such as hydrocarbons.

In particular, the present invention relates to a rotary bit adapted to break up the bottom of the hole being drilled by high-velocity high-pressure liquid jets that are directed onto the bottom of the hole by means of nozzles. The high-pressure liquid of the jets penetrates the pores of the formation and/or the cracks therein, consequently breaking up the formation. The fragments of the bottom of the hole are carried upwards by the liquid returning to the earth surface.

The nozzles are distributed over that part of the bit that faces the bottom of the hole when the bit is in operation. Since the bit is rotated around the central axis thereof, these nozzles travel over circles concentric with the central axis. In known bits, the nozzles when in operation, leave concentric ridges on the bottom of the hole, which ridges are broken up by mechanical means arranged between the nozzles. Such means may be bars of wedgeshaped elements that crumble the ridges, whereafter the fragments are carried upwards through the hole by the liquid flow returning to the earth surface. It will be appreciated that such mechanical means are liable to extreme wear and consequently shorten the operational life of the bit considerably.

Object of the invention is a rotary bit for drilling holes into underground formations by means of nozzles from which liquid is jetted against the bottom of the hole being drilled, which nozzles are arranged such that the circular ridges left on this bottom are of extremely small size and need not be broken up by mechanical means to allow the bit to proceed on its downward movement in the formation.

SUMMARY OF THE INVENTION According to the invention. a rotary bit for hydraulically drilling holes into underground formations comprises a bit body having a central axis and a plurality of nozzles mounted in one end of the bit body, the centres of the outlet openings of the nozzles being arranged on circles concentric to the central axis, the distance between the intersections of adjoining circles with a plane through the central axis being not greater than 3/2 (d, +11 wherein a, and d are the diameters of the nozzles on these adjoining circles, each nozzle having a central axis crossing the central axis of the bit body at an angle other than 90 and being arranged tangentially to a mathematical cone having a central axis coinciding with the central axis of the bit body, said cone having the apex thereof above the end of the bit body in which the nozzles are mounted, the apex angles of adjoining cones not differing more than 14, and the largest apex angle being over 90.

The invention will be described hereinafter in more detail with reference to the drawings which show by way of example some embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. I shows schematically a cross-section of a rotary bit according to the invention having a single row of nozzles;

FIG. 2 shows a side view of the bit according to FIG. I, taken in the direction of arrows 22;

FIG. 3 shows a bottom view of the bit according to FIG. I;

FIG. 4 shows schematically a cross-section of a rotary bit of the type shown in FIG. I but having a partially flat bottom part in which the nozzles are arranged;

FIG. 5 shows schematically a side view of a bit ac cording to the invention, the bit having a spherical bottom part;

FIG. 6 shows a bottom view of the bit according to FIG. 5 viewed in the direction of arrows 5-5',

FIG. 7 shows a side view of a rotary bit according to the invention, in which the bit body carries diamonds for cutting those formation parts that are of extreme hardness;

FIG. 8 shows a bottom view of the bit shown in FIG. 7 viewed in the direction of arrows 77; and

FIG. 9 shows on a large scale a longitudinal section of a nozzle that may be used in rotary bits according to the invention.

The bit according to the invention and shown in FIGS. 1-3 comprises a bit body I having a central axis 2. The upper end of the bit body I is provided with a screw thread 3 for connecting the bit to a drill collar string (not shown). The interior 4 of the bit body I communicates with an opening 5 adapted for communicating with the interior of the drill collar string when the body I is screwed onto this string.

Nozzles 7 are arranged in the bottom end 6 of the bit body 1, these nozzles allowing the liquid that has been passed from the interior of the drill collar string into the interior 4 of the body I to escape from the body I in the form ofa plurality ofjets 8. The direction of the jets 8 is indicated by the central axes 9 of the nozzles 7. In this particular embodiment of the invention, the axes 9 lies in a common plane and all axis intersect the central axis 2 of the bit body 1 at a common point. The centers of the outlet openings of the nozzles 7 are located on circles A, B, C, D......I, which circles are concentric to the central axis 2 of the body I. The distance between the intersections of adjoining circles with a plane through the central axis 2 is three times the diameter d of the outlet of the nozzles 7. These intersections are indicated in FIG. I by the points A, B, C, D ..,l'. Since the nozzles, arranged on circles of increasing diameter, are alternately placed at one side or the other side of the central axis 2, the distance between the centers of adjoining nozzles 7 is six times the diameter d. The nozzle 7 which is nearest to the central axis 2 is arranged at a circle with radius 1.5d.

It will be appreciated that on rotation of the bit around the central axis 2 thereof, the liquid jets will move over tracks having center lines coinciding with the circles A, B, C .J, and attack the bottom of the hole being drilled. The relative positions of the liquid jets during rotation of the bit are indicated by the arrows 8 and 8A (the latter being dotted). Arrows 8A show the position of the jets 8 relative to the bottom part 6 of the bit body when the bit has been rotated over As can be seen from FIG. I, the jets 8 are not parallel to the central axis 2 of the bit body I, but are each ar ranged at a certain angle thereto. The angle between each pair of adjoining arrows 8 and 8A is 5. Thus, the angle between the central axes 9 of adjoining nozzles 7 in the bottom part 6 of the bit body is 10. The central axes 9 are arranged on mathematical cones having central axis coinciding with the central axis 2 of the bit body I. The apex angles of adjoining cones differ degrees. This arrangement of the nozzles brings the outer jet 8" at an angle of 475 with respect to the side wall of the borehole being drilled, which angle is sufficiently great to remove part of the side wall just above the bottom of the hole to allow the passage of the body 1 through the hole. The angle between the axis 9" of the jet 8" and the central axis 2 of the bit body 1 is fairly large (i.e., larger than 45), but the angles between the various axes 9 of the jets 8 are relatively small, and this, in combination with the distance between the centers of the outlets of the nozzles 7 being equal to six times the diameter of these outlets, allows the passage of the bit body I through the hole and at the same time prevents the formation of annular ridges on the bottom of the hole, which ridges would have to be broken up by mechanical means such as bars or wedge-shaped members.

It will be appreciated that during such drilling operation, there is no physical contact between the bit body I and the bottom of the hole being drilled.

The bottom part 6 of the bit body 1 or the nozzles 7 are made of wear-resistant material. Various nozzle shapes may be applied. One nozzle design will be described hereinafter with reference to FIG. 9.

FlG. 4 shows a section over a bit similar to the bit 1, but having a partially flat bottom part 10 curved at the ends ll thereof. As in the design of the bit shown in FIGS. l3, the bit according to FIG. 4 comprises a sin gle row of nozzles 12 in the bottom part thereof. The distance between the centers of the outlets of adjoining nozzles 12 is five times the diameter of these outlets. Consequently. the distances between the intersections of adjoining circles on which the nozzles are located with a plane through the central axis 13 are 2.5 times the diameter of the outlets of the nozzles. The central axis 14 of the nozzles 12 are arranged on mathematical cones having apex angles which differ between 8 and 13 for each adjoining pair of cones. The largest apex angle of the cones is 98.

The central axes 9 and 14 of the nozzles 7 and 12, respectively, shown in FIGS. 1 and 4 are all in a common plane passing through the central axes 2 and 13, respectively, of the bits shown. However, the invention is not restricted hereto as can be seen from FIGS. 5 and 6 showing a side view and a bottom view, respectively, of a bit according to the invention, having the nozzles 15 thereof distributed over the bottom part 16 of the bit body 17. which bottom part is spherically shaped. The central axes (not shown) of all the nozzles 15 intersect the central axis l8 of the bit body 17. Each of these axes lies in the surface of a mathematical cone having the central axis thereof coinciding with the central axis 18 of the bit body 17. The apex angles of adjoining cones differ 14 and the distance between the intersections of adjoining circles on which the nozzles 15 are situated, with a plane through the central axis 18, is 2.5 times the outlet diameter of the nozzles 15. The largest apex angle is 104.

Extremely hard formation layers may resist the ac tion exerted thereon by the liquid jets and prevent passage of the rotary bit according to the invention therethrough. To obviate such problem, the nozzle arrangement according to the invention may be combined with a rotary bit suitable for drilling a hole in such hard formation by mechanical action. Preferably, a diamond bit is chosen for this purpose. A combination ofa diamond bit and the nozzle arrangement according to the invention is shown by way of example in FIGS. 7 and 8 of the drawing. The bit body 20 comprises a sintered mass 21 having diamonds 22 embedded in the surface thereof in a manner allowing cutting or scraping of the wall and the bottom of a hole in which the bit body is rotated. The body further comprises a screw coupling 23 for connecting the body 20 to a (not shown) drill collar string. The diamonds are arranged in rows, these rows being located between water channels 24 via which liquid is supplied to the space between the bit body 20 and the wall and the bottom of the hole in which this bit is being operated. The body 20 further comprises liquid jet nozzles 25 mounted in the bottom parts of the water channels 24 such that the nozzles 25 are not in contact with the wall and bottom of the borehole when the bit is being operated in the hole to mechanically break up hard formation layers by the action of the diamonds. During such operation the diamonds are in contact with the wall and bottom of the borehole and liquid for cooling and cleaning purposes is supplied to the water channels 24 via the nozzles 25.

The nozzles 25 communicate with the interior (not shown) of the bit body 20, and are distributed over the surface of the bit body 20 in the manner shown in FIG. 8. The nozzles are distributed over circles concentric to the central axis 26 of the bit body 20. Each circle (except the circle with the smallest diameter) has four nozzles located thereon. The distance between the intersections of adjoining circles with a plane through the central axis 26 is equal to the distance between adjoining nozzles that are arranged in a single row. This distance is two times the outlet diameter of the nozzles 25. Further, the central axis of the nozzles need not be in the surfaces of the cones. The same results will be obtained when these central axis are arranged tangentially to the cones and cross the central axis of the bit body at an angle other than The jets issuing from the nozzles then cut in or contrary to the direction of movement of the nozzles over the tracks thereof when the bit is rotated during the drilling operation.

The bit body parts in which the nozzles are formed may be of a wear-resistant material. In another embodiment of the invention, the nozzles are separately shaped in the form of insert pieces of wear-resistant material, which pieces are placed in the wall of the bit body, preferably by brazing.

The diameter of the nozzles is between 0.8 and 8 millimetres. Preferably, the diameter of the outlet of the nozzles is between 1.5 and 4 millimetres. The nozzle shape may be of any design suitable for the purpose. One such design is shown in FIG. 9. The nozzle 30 is formed in a insert piece 31. The outlet 32 has a diameter d and the inner wall 33 is conically shaped and has an apex angle of 10. The inlet 34 of the nozzle has a curvature R d and the nozzle length L 3.1 d.

The nozzles shown in the various bits described above have the same diameter per bit. However, the invention is not restricted hereto. If in a single bit nozzles of different diameter are applied, the distance between the intersections of adjoining circles on which the nozzles are arranged with a plane through the central axis of the bit body should not be greater than 3/2 (d' d when the diameter of the outlet(s) of the nozzle(s) arranged on one of the adjoining circles is d, and the diameter of the outlet( s) of the nozzle( s) arranged on the other of the adjoining circles is d The distances between the above-mentioned intersections need not necessarily be equal to each other. One or more nozzles may be located on each circle.

The central axis of the nozzles (or the jets issuing therefrom) are each arranged in the surface or tangentially (provided that the angle at which a central axis of a nozzle crosses the central axis of the bit body is different from 90) to the surface of a mathematical cone having the central axis thereof coinciding with the central axis of the bit body. The difference between the apex angles of adjoining cones is at most 14. The largest apex angle of the cones should be over 90". Preferably, this larges apex angle is less than I l0.

The differences between apex angles of the various pairs of adjoining cones need not necessarily be equal to each other.

It will be appreciated that the nozzles having the centres of the outlet openings thereof arranged on the concentric circle having the largest diameter are placed sufficiently close to the rim of the bottom portion of the bit to allow the hole to be cut at a diameter larger than the largest diameter of the bit body. As already explained above, these nozzles have the central axis thereof directed at an angle over with respect to the central axis of the bit body. The relatively small differences between the apex angles of the matmatical cones on which the other nozzles are located, as well as the relatively small distances between the intersections of the circles on which the outlet openings of the nozzles are arranged with the central axis of the bit body, allow the bottom of the hole that is being drilled to be broken up without any major annular ridges being left. Only those bits that have to be operated in formations where extremely hard layers of limited thickness are present. may require cutting means to break up those layers. These cutting means are designed for cutting the total surface of the bottom of the hole, and do not need the assistance of the hydraulic jets, other than for cooling and cleaning purposes.

We claim as our invention:

1. A rotary bit for hydraulically drilling holes into underground formations, said bit comprising a bit body having a central axis and a plurality of nozzles mounted in one end of the bit body, the centres of the outlet openings of the nozzles being arranged on circles concentric to the central axis, the distance between the intersections of adjoining circles with a plane through the central axis being not greater than 3/2 (d d wherein d; and d are the outlet diameters of the nozzles on these adjoining circles, each nozzle having a central axis crossing the central axis of the bit body at an angle other than and being arranged tangentially to a separate mathematical cone having a central axis coinciding with the central axis of the bit body, said cone having the apex thereof above the end of the bit body in which the nozzles are mounted, the apex angles of adjoining cones not differing more than 14, and the largest apex angle being over 90. and wherein the apices of the mathematical cones line in a common point on the central axis of the rotary bit, said bit having a lower surface arcuate in form, the centres of the outlet openings of the nozzles being arranged in said arcuate lower surface.

2. A rotary bit according to claim 1, comprising cutting elements for mechanically cutting the total surface of the bottom of a hole being drilled by the bit. 

1. A rotary bit for hydraulically drilling holes into underground formations, said bit comprising a bit body having a central axis and a plurality of nozzles mounted in one end of the bit body, the centres of the outlet openings of the nozzles being arranged on circles concentric to the central axis, the distance between the intersections of adjoining circles with a plane through the central axis being not greater than 3/2 (d1 + d2), wherein d1 and d2 are the outlet diameters of the nozzles on these adjoining circles, each nozzle having a central axis crossing the central axis of the bit body at an angle other than 90* and being arranged tangetially to a separate mathematical cone having a central axis coinciding with the central axis of the bit body, said cone having the apex thereof above the end of the bit body in which the nozzles are mounted, the apex angles of adjoining cones not differing more than 14*, and the largest apex angle being over 90*, and wherein the apices of the mathematical cones line in a common point on the central axis of the rotary bit, said bit having a lower surface arcuate in form, the centres of the outlet openings of the nozzles being arranged in said arcuate lower surface.
 2. A rotary bit according to claim 1, comprising cutting elements for mechanically cutting the total surface of the bottom of a hole being drilled by the bit. 